Convert HTML code of single quote (i.e. ') to text

I don't see why this is an issue for you. & is the right
representation, the browser takes care of rendering that as a quote.
You need to see what you are doing with the incoming data before
displaying it. Also, have a look at html_escape() / h() helper
function and sanitize data before database insertion. You shouldn't
be storing a & into the database text field.